Moderate-to-vigorous physical activity (MVPA) is associated with a multitude of physical and mental health benefits, yet fewer than half of school-aged children achieve the recommended 60 minutes of daily MVPA. Only 12 percent of states mandate the Institute of Medicine's (IOM) recommendation of 150 minutes of physical education per week at the elementary level, despite a positive association between MVPA and academic achievement. Further, disparities in physical activity (PA)-supporting policies, activities, and environments between lower-socioeconomic status (SES) schools compared to higher-SES schools, may result in even fewer minutes of school-time MVPA for lower-SES children. Adaptable and scalable school-based PA programs are needed to address disparities in PA opportunities available to underserved schoolchildren in socioeconomically disadvantaged and racially diverse school districts. In the fall of 2013, the Active Schools Acceleration Project (ASAP) provided 700 U.S. elementary schools with micro-grants to implement award winning school-based PA programs during the 2013-2014 school year, either 1) The 100 Mile Club, a walking and running program offered throughout the school day, or 2) Just Move, a classroom-based PA break program. In the 2014-2015 school year, these programs will be further expanded nationwide; however their impact on increased MVPA and academic success among underserved children has yet to be rigorously evaluated. The overall objective of this application is to examine the impact of two PA programs implemented in elementary schools, 100 Mile Club and Just Move, on physical activity engagement and academic success in underserved schoolchildren in a randomized controlled study. Outcomes of interest include school-time and total daily MVPA, cognitive performance, and academic achievement. We will further examine child-level correlates of PA program participation and school-level correlates of program reach. We propose to assess these outcomes by studying children in schools implementing either 100 Mile Club (n=7) or Just Move (n=7) compared to control schools (n=7) within underserved school districts with high obesity rates in Massachusetts. Outcomes will be assessed at 5 months and 1.5 years using accelerometry, a standardized cognitive performance assessment, and standardized test scores. This randomized and controlled study will answer the important question of whether school-based PA programs are an effective strategy to improve daily MVPA and academic success among underserved schoolchildren.